The present invention relates to a mass spectrometer, a method of mass spectrometry, an ion trap and a method of trapping ions. 3D or Paul ion traps comprising a central ring electrode and two end-cap electrodes are well known and provide a powerful and relatively inexpensive tool for many types of analysis of ions.
2D or linear ion traps (“LIT”) comprising a quadrupole rod set and two electrodes for confining ions axially within the ion trap are also well known. The sensitivity and dynamic range of commercial linear ion traps have improved significantly in recent years. A linear ion trap which ejected ions axially (rather than radially) would be particularly suited for incorporation into a hybrid mass spectrometer having a linear ion path geometry. However, most commercial linear ion traps eject ions in a radial direction which causes significant design difficulties.
It is therefore desired to provide an improved ion trap wherein ions are ejected axially from the ion trap.